Front end alignment on fabbed front ends….hows it done?

[Jonny Hotnuts]

It is not like I can take the car to a local alignment shop. Is there a common procedure for getting both wheels pointing forward?

[sheribuchta]

Hey Jonny,
We sent you a book today priority mail. Sorry about the delay but Willie had to find the book first. We have been remodeling and everything is packed. It's kind of a hot rod - drag race thing but you should be able to figure out everything you need to know. If you need any more info let us know.

Willie and Sheri Buchta

[Stainless1]

JNuts, make sure the back wheels are pointed correctly first.  Old 8 ft florescent tubes are generally straight.  You can also find cheap laser levels almost anywhere. If you figure out the backs are pointed straight, then point the fronts the same way.  After you get the fronts straight, add an equal amount of toe-in to each.  Roll it down the street, have someone hold the wheel straight, while you watch after you are done.  If it looks a little crabbed, start over.

[Sumner]

......... Old 8 ft florescent tubes are generally straight.  You can also find cheap laser levels almost anywhere. If you figure out the backs are pointed straight, then point the fronts the same way.  After you get the fronts straight, add an equal amount of toe-in to each...............

Good stuff.....




............ while my car is still on the build table  and I could measure off of the center-line down the table I made removable brackets that let me "string" both sides on the car.  It seems to be working, but my car hasn't moved and
Stainless's has  , so pay attention to what he has to offer  .

More on what I did here............

http://purplesagetradingpost.com/sumner/bvillecar-2/construction%20page-79.html

........... c ya,

Sum

[Jonny Hotnuts]

After you get the fronts straight, add an equal amount of toe-in to each

Why would you want any toe-in?

[Stainless1]

a 1/16 to an 1/8 total toe in keeps your front end from searching.  If you ran last year without any toe-in, that may have caused your handling problems...

[Sumner]

After you get the fronts straight, add an equal amount of toe-in to each

Why would you want any toe-in?

No matter how good/new all of the steering components are there is going to be some clearances built into them that will cause some slack.  The tendency for a car in motion is for that slack to cause the wheels to toe-out, so you are trying to compensate for that by toeing them in so that under way they will actually be straight.  Since you don't know precisely how much is needed it is better to have a little too much toe-in, so that they still might be toed in to create the situation Stainless is talking about.

Sum

[836dstr]

If you have a chassis mounted rack & pinion you might want as much as 3/8's total depending on geometry and suspension travel. A R&P mounted to the axle eliminates this need. This applies to a one piece axle and not IFS.

[V4F STR 60]

Why 3/8" toe-in on a chassis mounted rack and pinion?  Does this hold true if I have a front panhard bar?  Thank you, Pedro

[Peter Jack]

I don't think you'll want a chassis mounted rack. To see why mount the rack in its approximate position and hook up the steering linkage. With the springs removed move the axle up and down in its range of travel. Include a little sideways roll for interest. Carefully measure the steering angle of the wheels while you do this. What you're measuring is bump steer or roll steer and it can lead to some very interesting handling.

Pete

P.S. Mounting the rack on the axle will eliminate most of this motion. You'll still have to watch out for variations on akkerman or toe change when the wheels are turned.

P.J.

[V4F STR 60]

Thanks,  I'll remove the spring and check out the bumpsteer today.  Good thought, even though I tried to address when I built it by making sure the drag link (If that's what you still call it on a rack) was horizontal at ride height.  I am trying to sort out my handling issues before WF.  We have the speed, but that doesn't do much if the car prefers turning around... and I don't want to have another coaching session from the safety steward (he was just doing his job).  My other thoughts/concerns are too much Ackerman, no front panhard, flex in the long front wishbones...

Thanks again, Pedro

[RichFox]

On my car I have a shackle on the left side of the front axle only. This negates the need for a panhard bar. Suspension travel has not been enough at Bonneville to cause any bump steer. It has early Ford type steering. On my coup I did mount the R&P to the axle. Not sure why a chassis mount would seem better.

[Peter Jack]

Just to add to the quick note on checking bump steer, I usually clamp the rack by pulling back the rubber boots and using vise grips to hold a small piece of protective aluminum at each end of the housing so there is no back and forth movement in the rack and pinion while i'm jacking the axle up and down.

Pete

[JimL]

...when your sure it's right, and up on wheels, pour a puddle of water on flat floor (each side), then roll the tires through it.  Compare the track patterns on both sides (front to rear) to find dog-tracking or crabbing.  If you have suspension, add all the weight you can (family, friends, neighbors) and roll through the puddles.  If something changes, it's time to sit down and THINK HARD!!

I've used this simple test to "kick back" the Hunter rep when he's convinced there's nothing wrong with his installation and calibration.  It's pretty hard to argue with the actual rolling tire tracks!

[427MG]

I don't think you'll want a chassis mounted rack. To see why mount the rack in its approximate position and hook up the steering linkage. With the springs removed move the axle up and down in its range of travel. Include a little sideways roll for interest. Carefully measure the steering angle of the wheels while you do this. What you're measuring is bump steer or roll steer and it can lead to some very interesting handling.

Pete

P.S. Mounting the rack on the axle will eliminate most of this motion. You'll still have to watch out for variations on akkerman or toe change when the wheels are turned.

P.J.

I can confirm that if you have a set-up with a chassis mounted rack and a beam or tube axle the steering characteristics are 'interesting'. My MG used to have a 6" drop tube with a full width, chassis mounted R&P. If you turned the steering wheel on my beasty more than a 1/4 turn the geometry went all over the place and the bump steer, the scrub and everything else made it near impossible to drive. The final straw came when hitting a pot-hole whilst on full right lock, the suspension went on full lift whilst on full lock and promptly stayed there when it all got past it extremes. A heart stopping moment!

It's all gone and I've now made my own IRS that actually works with proper geometry.